Acoustic horn



Feb. 18, 1930. H. c. HARRISON 1,747,830

ACOUSTIC HORN Filed Oct. 6, 1928 3 Sheets-Sheet '1 /Nl EN 70/? h! C. HAHHVSON ATTORNEY Feb. 18, 1930. H. c. HARRISON ACOUSTIC HORN 3 Sheets-Sheet 2 Filed 001;. 6, 1928 A r TURN/5) H. C. HARRISON ACOUSTIC HORN Feb. 18, 1930.

Filed Oct. 6, 1928 3 Sheets-Sheet 5 lNl/ENTOI? hi E1 HARRISON 5y ATTORNEY 45 used for phonographs. .The soun Patented Feb. 18, 1930 UNITED STATES PATENT OFFICE HENRY O. HARRISON, OF PORT WASHINGTON, NEW YORK, ASSIGNOR TO BELL TELE- PHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK Application filed October 6, 1928, Serial No.

This invention relates to acoustic horns, and has for its object to secure compactness in "the construction of horns whereby they may more readily be mounted in cabinets of relati'vely small dimensions. The subject matter of this application relating to the broad features of the invention is disclosed in my co-pending application Serial No. 628,168, filed March 28,1923, and the subject matter relating to the application of the invention to a phonograph horn is disclosed in my co pending application Serial No. 33,619, filed Ma iy 29, 1925. f be compact form may be obtained by providing a reentrant horn in which the sound waves traverse the space withinthe enclosing walls a plurality of times and expand progressively at a suitable rate in their passage therethrough. One form of compact structure may be produced by dividing a chamber, constituting the bell or flare portion, into two tapering passages by means of a partition within which are located two tapered passages constituting the body or intermediate portion of the horn, these passages opening at their larger ends into the smaller ends of the passages constituting the bell, and at their smaller ends intoa tapered portion forming the neck or-throat of the horn. The throat portion of the horn may extend from a point within the partition member through the rear enclosing wall of the bell to a loud speaking telephone receiver or to the tone arm-of a mechanical phonograph. When the folded horn of the invention is used in connection with a mechanical phonograph, it may be mounted in a cabinet underneath the platform on which the record table is mounted, in which casethe throat portion may be brought out through the upper wall of the bell and ledup to a tone arm coupling in theplatform.

The method of construction enables horns of great length and large mouth opening to be assembled in cabinets of the size dgenerally passage preferably has its cross-sectional area tapered according to an exponential law, in the manner explained in my copending application Serial No. 225,500, filed October 11, 1927.

This not only improves the acoustical qualiacousrxc norm 310,750, and in. Germany October 21, 192 8.

cross-sectional area.

Fig; -1 is a perspective view, partly in section, of a horn embodying the invention;

Fig.2 is a sectional view through the center of the horn along the line 22 of Fig. 3; and Fig. 3 is a sectional view along the line 3-3 of Fig. 2. Figs. 4 and 5 illustrate an adaptation of the invention to a phonograph. Figs. 6, 7 and 8 illustrate another embodiment of the invention, Fi 7 being a sectional view of the horn along t e line 7-7 of Fig. 8 which is a sectional view along the line 88 of Fig. 7.

Figs. 1, 2 and 3 illustrate the invention in a preferred form and show the paths of the sound waves. The horn is contained in a bell portion rectangular in cross-section having two parallel walls 51-and 52 and two walls 53 and 54 divergent from a back 55. The back 55 is formed with a transverse inwardly projecting ridge 56 on the inside .extending across the bell midway between the divergent walls and parallel thereto. Extending between the parallel walls, in front of the ridge 56 and spaced therefrom except at, the center, is a partition 57 dividing the bell into two equal chambers 58 and 59-. Within the partition 57 are two curved channels 60, and 61 branching symmetrically to each side from a central throat 62 and turning rearwardly towards the ridge 56 where they connect with the chambers 58 and 59. The throat 62 extends through a heart shaped piece formed in the center of the partition by passages and 61 to the back 55 of the bell and terminates in a neck 63 to which a loud speaking receiver may be connected. Each of the channels 60 and 61 communicates with both chambers 58 and 59of the bell. .The paths of the sound waves are indicated by the arrows. i In the horn shown, the sound waves enter:

ing the throat or the primary portion 62 are divided and reflexed through an angle of approximately 180 by the intermediate portion or chambers 60 and 61 in which the wave front expansion is practically all in one di- 'mension there being little or no expansion in the other dimension. At the exits of chambers 6.0 and 61 the sound waves are turned forward again through an angle of approximately 180 into the bell portion or chambers 58 and 59 in which the wave front expansion is practically all in one dimension and perpendicular. to the wave frontexpansion in chambers 60 and 61. The walls 64 and 65 are common to the intermediate portion containing chambers 60 and 61 and the bell portion containing chambers- 59 and '58. In both of the chambers 60 and 61 they define two opposite walls and in each of the chambers 58 and 59 they define but one wall respectively. By providing two intermediate chambers the sound wave fronts may be expanded to substantially the full width of the bell portion between its parallel walls without becoming deeply curved thereby mini-r mizing the phase displacement at the entrance of the bell portion.

The wave front expansion in the outlet chamber 58 takes place between the diverging walls 54 and 64 and in chamber 59 between the diverging walls 65 and 53, the walls 52 and 51 being substantially parallel.

Although it maybe desirablethat the horn be made symmetrical, this is not essential. The progressive horn areas can be made with the desired degree of increasing values even though one of the tortuous paths is made larger in cross-sectional area than the other; In this case, the intermediate partition is not centrally located.

Figs. 4 and 5 illustrate the application of. the invention in a stylus operated phonograph. The horn is housed within the phonograph cabinet beneath a platform '68 in the upper portion thereof on which is mounted the tone arm66 and the record turntable 67. The horn is essentially similar to that of Figs.- 1 to 3, but is modified in such a way that the throat 62 instead of pro ecting through the back of. the bell passes through the upper wall of thepartition member 57 and is carried upward through one wall 53 of the hell by a curved neck portion 69 to the platform68 where it connects with the tone I vided at the mouth of the horn, which may be arm 66. Swinging doors-90' and 91 are proclosed when the horn is not in use. In the illustration an unsymmetrical horn is shown, the lower portion 58 ofthe bell being greater in cross-sectional area than the upper portion 59.} This will frequently be found convenient for use in existing types of phonographs in which the upper doors are smaller I than the flower ones. Furthermore, it is found that a slightly greater efiective horn length may be obtainable by the use of the dissymm'etrical form. The horn fills the entire compartment of the phonograph beneath the su porting platform 68 for the record table 6 and tone arm, and has an effective length more than twice the physical length .of the cabinet from front to back. Such a born, by virtue of the method of folding can be adapted to fit in many forms of cabinet, thereby enabling the advantages of great length and large mouth opening to be obtained in a relatively small cubic space.

In Figs. 6, 7 and 8' is illustrated another form of horn embodying the invention. The horn is contained in a bell portion rectangular in cross-section consisting of the four walls 70, 71, 72 and 73 and a back 7%. The walls 72 and 7 3 are parallel, and perpendicular to the back 7 4. The wall 71 is divergent from the back with respect to the wall "which is perpendicular to the back. At-

tached to the wall 70 is the portion 75 con.- v

invention. For example, some of t e walls are shown parallel and perpendicular to the back. This is not an essential feature, as a horn having tlfe proper progressive increase in cross-sectional areas can be made with some other arran ement of walls.

What is claime 1s:

1. A horn having a bell portion, apartition dividing said bell portion intotwo. cham- 5 bars, a pair'of channels in said partition intermedlate said chambers and communicating therewith and a throat portion communic'ating withsaid channels.

- 2. A horn having a bell portion, a partition dividingsaid bell portion into two equal chambers, a pair of similar channels symmet- ,rically disposed within said partition, each channel communicating with both of saidchambers, and a throat-portion common to said channels.

'3. A horn comprising a bell portion, a par- I tition dividing said bellportion into two similar chambers, channels. in said partition opening rearwardly, a ridge in said bell portion bisecting the openings in said channels,

and a throat through said ridge communicatmg with said channels.

. 4. A horn comprising a bell portion having two chambers, a body portion. hav ng two channels joiiitly communicating with said chambers, the plane of expansion of the sound wave fronts in the channels of body portion being at right angles to the "plane of expansion of the sound wave fronts in the supported by and extending'between oppo-' site walls of said bell portions, said intermediate portion .consisting of two oppositely curved substantially flat chambers having one wall in common with said bell portion.

7 A horn having a bell portion of rectangular cross section, a throat portion, and an 7 intermediate portion of rectangular cross section connecting said bell and throat portions and having substantially parallel opposite walls, said intermediate portion being curved through an angle of approximately 180 between said walls. I

i 8. A horn comprising a bell portio having two parallel walls and two dlvergi g walls,

a throat portion, and an intermediate por-- tion comprising two similar r'eversely curved sound passages of rectangular cross-section connecting said throat and bell portions, said intermediate portion having diverging walls for expanding the sound wave fronts in one dimension to substantially the width of the bell portion between the parallel walls with substantially no expansion in the other dimension.

9. A horn comprising a main portion having a curved rear wall, a throat and a thin expansion chamber having substantially parallel walls for connecting said throat and said main portion, said chamber being curved through an angle of substantially 180 between its parallel walls and adapted to direct Y the sound waves against said curved wall.

10. A horn comprising a bell portion having flat oppositely diverging walls, a throat portion, and an intermediate portion between said diverging walls connecting said bell and throat portions said intermediate portion having substantially parallel walls and curved through an angleof approximately 180? between said walls.

11. A horn comprising a'bell shaped portion of rectangular cross-section having diverging walls, a throat portion and a sub stantially flat intermediate portion'of rec: tangular cross-section connecting said bell and throat portions, said intermediate portion being curved through an angle of approximately 180 and having one wall in common with said bell portion.

12. A horn comprising an outlet chamber having parallel and diverging walls, a throat ortion and a substantially fiat rectangular intermediate portion curved through anangle of approximately 180 in a plane perpendicular to the parallel walls of said chamber and disposed substantially fiat-against one of the diverging Walls of said chamber.

13. A horn comprising an outlet chamber of rectangular cross-section, and a substantially flat portion of rectangular cross-section communicating therewith and curved through an angle of approximately 180 in a plane substantially parallel to and in contact with one side of said chamber.

14. A compact horn comprising an outlet chamber having four walls (51, 52, 53, 65) and an adjacent sound passage (61") opening into said chamber, said sound passage having one wall member (65) in common with said chamber, the n1aj0r .expansion of said chamber and said sound passage being in directions at right angles to each other.

15. A horn comprising a thr0at portion, an intermediate portion having two chambers, one end of each chamber communicating with said throat portion, and a bell portion having two chambers, each chamber of said bell portion communicatingwith the other ends of both of the chambers in said intermediate portion.

16; A phonographcomprising a tone arm and a horn having a rectangular bell portion, an intermediate portion dividing said bell portion into two sections, and a third portion connecting said intermediate portion to said tone arm, said third portion extending through one of the sections of said bell portion.

17. A phonograph in accordance with the preceding claim, wherein each section of the bell portion has a diiferent mouth opening.

- 18. Aphonograph comprising a tone arm and'a horn having a rectangular bell portion and a third portion connecting said born to saidtone arm, said third portion extending through two walls of said bell portion.

19. The combination with a phonograph or like cabinet, of a sound amplifier divided and leading upwardly therefrom to the open-.

ing of the sound conduit and ahead of the rear walls of the flare portions.

20. The combination with a phonograph or like cabinet, of a sound amplifier having two flare portions opening through thefront of 7 the-cabinet and extending approximately to the rear thereof, a sound conduit having an opening through'the top wall of thecabinet near the rear thereof, an intermediate tapered portion connected with the flare portions, and a neck portion connected centrally of said intermediate portion and extending upwardlytosa-id conduit opening, ahead of the-rearof the 'flarin passa es. -21. Inaphonograp in com ination,acab1- net, a record and tone arm platform for said cabinet located near the upper end thereof, a -tone arm. on said platforma'nd opening through the vplatform near the rear of the cabinet and a horn located in the cabinet below the platform, the horn comprising a neck portion and a folded portion combined to give an over-all length equal to substantiall the depth of the cabinet from front to bac andan eifective length for sound amplifica. tion equal to two or more times the depthof the cabinet from ifron't to back, the neck oi-1- tion connectin at its uplperend with the tone arm opening t rough t e platform and lying within'vertical planes defining the depth of r the born from front to back of the cabinet and the folded portion of the horn being located between horizontalplanes defining the extent of the mouth opening of. the horn.

22. In a phonograph in "combination, a cabinet, 'a' horizontally: arrangedrecord and tone armsupporting-platform in'the cabinet having an opening therethroug'hxlior one end of the tonearm, an'd'ja horn or sound amplifier in said cabinet below the platform and comprising two substantially semi-circular 0 passages atri'ght angles' toone another, the neck of said horn being connectedwithj the v tone 'arm opening in theplatform landrthe mouth of said .horn opening-througha side Y wall of the cabinet. 5 -f' 1 "a5 23QA honograph according to'claim 22 wherein t plane of one of the bends of the. horn is substantially- .vertical and the plane of the other bend is substantially horizontal. 24,-"In a phonograph in combination, a T40 cabinet, a tone arm, a supporting platform therefor, a hornhaving a greater effective length thanover-all length and including a flare and aneck portiont extending through one wall of the horn into engagement with the 5 tonearmpf' 9 w 25. A horn comprising a bell ortion, an inlet portion communicating the rear of said bell portion and dividing it into two separate chambers, said inlet'portion extendao ing forwardly and then rearwardly between *saidchambers' 7 .L- p f 1 26.,A horn comprising a bellportion hav- -ing two'outletchambers tapering fromfront v .to rear; anintermediate portion lying be- '-5'5 tween the fronts I and backs of said outlet chambers, said intermediate portion havinginlet and outlet openings, the outlet opening being near 'thez'rear of said-outlet chambers, 1 2 and a throat'jportionbetween saidchambers and associated the inlet opening of said [intermediate portion. v

;In witness whereof, I hereun subscribe my name this.5th day-of;0ctobe'f,* 928.

4:5 HARRISON. 

